Subscriber Identity Module Cards (SIM cards) are equipped and used in mobile terminals such as mobile telephones. A SIM controller installed in a mobile terminal controls data communication with the SIM card (see, for example, Japanese Laid-Open Patent Publication No. 2007-317170). Further, to reduce power consumption by a USB device, a suspend function is provided to the USB device (see, for example, Japanese Laid-Open Patent Publication No. 2008-84230). Recently, in SIM cards, an Inter-Chip (IC)-USB interface (I/F) is used. In this IC-USB, an I/F similar to a typical USB scheme I/F is used as the physical I/F between the SIM controller and SIM card, facilitating increased speed.
In the conventional technology above, the SIM controller has to frequently and quickly access the SIM card to access files, check for SIM card insertion, etc., the control of which is performed in a normal (resumed) state.
Meanwhile, in mobile apparatuses, such as mobile telephones, to reduce power consumption, it is desirable to maintain a low power consuming (suspended) state as much as possible. In this regard, consideration must be given to the point that in order to switch between suspended and resumed states, a fixed period is necessary for processing. With consideration of this point, when suspend control is performed, efficient suspend control is required. For example, when unnecessary suspended states occur frequently without performing suspend/resume control according to the access state of the SIM card, at each suspended state, it takes time to change between the suspended state and the resumed state. Further, during the time it takes to change states, the SIM card cannot be accessed, arising in a problem of a decrease in the overall efficiency in accessing the SIM card.
The conventional technology above does not consider the efficiency of control for changing between the suspended and resumed states of the SIM card and accordingly, accessing of files in the SIM card could not be made more efficient. Furthermore, decreases in power consumption could not be achieved.